Sources: National Statistical Office, Report of the Household Socio-Economic Survey, various issues.
a Since the data for 1981 are available only on an area-by-area basis, the average monthly incomes of non- agricultural occupations and agricultural occupations shown here are those in the urban area (with the
figures for Bangkok shown in parentheses) and the rural area, respectively.
b The figure for the self-employed professional and technical jobs in 1990 is not shown here because it is in-
consistent with the corresponding figures for other years and is thus deemed unreliable.
c It is not known why the 1986 and 1988 figures for proprietors decreased or remained low while those for
other occupations were on the increase.